CVE-2023-43635
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedVault Key Sealed With SHA1 PCRs The measured boot solution implemented in EVE OS leans on a PCR locking mechanism. Different parts of the system update different PCR values in the TPM, resulting in a unique value for each PCR entry. These PCRs are then used in order to seal/unseal a key from the TPM which is used to encrypt/decrypt the “vault” directory. This “vault” directory is the most sensitive point in the system and as such, its content should be protected. This mechanism is noted in Zededa’s documentation as the “measured boot” mechanism, designed to protect said “vault”. The code that’s responsible for generating and fetching the key from the TPM assumes that SHA256 PCRs are used in order to seal/unseal the key, and as such their presence is being checked. The issue here is that the key is not sealed using SHA256 PCRs, but using SHA1 PCRs. This leads to several issues: • Machines that have their SHA256 PCRs enabled but SHA1 PCRs disabled, as well as not sealing their keys at all, meaning the “vault” is not protected from an attacker. • SHA1 is considered insecure and reduces the complexity level required to unseal the key in machines which have their SHA1 PCRs enabled. An attacker can very easily retrieve the contents of the “vault”, which will effectively render the “measured boot” mechanism meaningless.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceThe vault key in EVE OS is sealed using SHA1 PCRs instead of the expected SHA256 PCRs. On systems with SHA256 PCRs enabled but SHA1 disabled, the key is not sealed at all, leaving the vault directory unprotected. SHA1's cryptographic weakness also reduces the effort needed to unseal the key.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 9.5.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Local
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Changed
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check EVE OS versionRun 'cat /etc/eve-version' or check the image metadata to determine the installed EVE OS versionAffected if Version is below 9.5.0
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Verify TPM PCR banksUse 'tpm2_pcrread' to list available PCR banks and identify which algorithms are enabled (SHA1 vs SHA256)Affected if SHA256 PCR bank is enabled but SHA1 PCR bank is disabled or not available
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Inspect vault key sealing configurationExamine the vault sealing configuration files or use tpm2 tools to read the PCR selections used when the vault key was sealedAffected if The vault key is sealed using SHA1 PCRs (PCR bank 4) instead of SHA256 PCRs (PCR bank 12)
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Verify vault directory protectionAttempt to access the vault directory or check if the vault is accessible without proper TPM unsealingAffected if Vault directory is accessible without requiring TPM-based authentication or unsealing
You are affected if running EVE OS below version 9.5.0 with SHA256 PCRs enabled but the vault key is sealed using SHA1 PCRs or is unprotected.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped9.5.0
Modify the key sealing logic to use SHA256 PCRs as intended, and implement proper validation that verifies the correct PCR bank is being used before sealing.
Edge Virtualization Engine 9.5.0 or later
- Upgrade Edge Virtualization Engine to version 9.5.0 or later to ensure the vault key is sealed with SHA256 PCRs instead of SHA1
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing12.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2023-43635 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2023-43635 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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